1. Field of the Invention
The present invention relates to a micromechanical pressure sensor device and to a corresponding manufacturing method.
2. Description of the Related Art
While any arbitrary micromechanical components may also be used, the present invention and the problems underlying the present invention are explained based on silicon-based components.
Micromechanical sensor devices for measuring acceleration, rotation rate, magnetic field and pressure, for example, are generally known and are manufactured for various applications in the automotive and consumer fields in mass production. Trends in the consumer electronics are in particular the miniaturization of the components, the integration of functions, and effective cost reduction.
Today, acceleration and rotation rate sensors and also acceleration and magnetic field sensors are already manufactured as combination sensors (6d), and additionally the first 9d modules are available, in which 3-axis acceleration, rotation rate and magnetic field sensors are combined in each case in a single sensor device.
In contrast, pressure sensors are developed and produced today separately from the above-mentioned 6d and 9d modules. One essential reason for this is the necessary media access which a pressure sensor requires, contrary to inertial and magnetic sensors, and which considerably increases the complexity and the costs for packaging the pressure sensor. Further reasons for separating pressure sensors are the different MEMS manufacturing processes and the different evaluation methods. For example, pressure sensors frequently employ piezoresistive resistors for evaluation, while inertial sensors are preferably capacitively evaluated.
However, it is foreseeable that sensor devices which, in addition to inertial quantities, are also able to measure the pressure represent an interesting extension of the options for functional integration, in particular in the field of consumer electronics. Such integrated 7d modules, or 10d modules with the integration of a 3-axis magnetic sensor, could be used for navigation applications (indoor navigation), for example. The functional integration promises both a cost reduction and a reduced space requirement on the application printed circuit board.
Micromechanical combination components including pressure and inertial sensors are known from published German patent application document DE 10 2006 011 545 A1 and US Patent Application Publication 2012/0256282 A1. All these components have in common that they use a capacitive evaluation principle in which a diaphragm to which pressure is applied warps and is used as a movable electrode surface. Spaced apart thereabove or therebeneath is a planar fixed electrode as the counter electrode. In such systems, the diaphragm warping is large in the central diaphragm area and drastically decreases toward the outside, to finally become zero at the edge of the diaphragm area. In the evaluation of the change in capacitance integrated over the diaphragm surface, significant diaphragm areas in the border area thus barely contribute to the signal deviation, while the central diaphragm areas which are subject to large deflections account for only a small portion of the overall surface.
Methods of so-called vertical integration or hybrid integration or 3D integration are known, in which at least one MEMS wafer and one evaluation ASIC wafer are mechanically joined and electrically connected to each other using wafer bonding processes, for example from U.S. Pat. No. 7,250,353 B2 or U.S. Pat. No. 7,442,570 B2. These vertical integration methods are particularly attractive in combination with silicon vias and flip chip technologies, whereby the external contacting may take place as a “bare die module” or “chip scale package,” i.e., without plastic packaging, as is known from US Patent Application Publication 2012/0049299 A1 or US Patent Application Publication 2012/0235251 A1, for example.
US Patent Application Publication 2013/0001710 A1 describes a method and a system for forming an MEMS sensor device, a handle wafer being bonded to an MEMS wafer via a dielectric layer. After the MEMS wafer has been structured to form the micromechanical sensor device, a CMOS wafer is bonded onto the MEMS wafer having the sensor device. At the end of the process, the handle wafer may be processed further by etching or back grinding, if necessary.